# A Proposal for the RNAome at the Dawn of the Last Universal Common Ancestor

## TL;DR

This paper proposes how ancient RNA molecules evolved into modern ones through two genetic code pathways, shaping essential RNA structures.

## Contribution

The paper introduces a novel evolutionary model for RNAome development using two extended genetic code pathways.

## Key findings

- RNA molecules contain regions encoded by both Extended Genetic Code 1 and 2.
- Essential RNA features like the Peptidyl Transferase Centre are better explained by Extended Code 2.
- Bacterial and archaeal RNA sequences show higher stability compared to controls.

## Abstract

From the most ancient RNAs, which followed an RNY pattern and folded into small hairpins, modern RNA molecules evolved by two different pathways, dubbed Extended Genetic Code 1 and 2, finally conforming to the current standard genetic code. Herein, we describe the evolutionary path of the RNAome based on these evolutionary routes. In general, all the RNA molecules analysed contain portions encoded by both genetic codes, but crucial features seem to be better recovered by Extended 2 triplets. In particular, the whole Peptidyl Transferase Centre, anti-Shine–Dalgarno motif, and a characteristic quadruplet of the RNA moiety of RNAse-P are clearly unveiled. Differences between bacteria and archaea are also detected; in most cases, the biological sequences are more stable than their controls. We then describe an evolutionary trajectory of the RNAome formation, based on two complementary evolutionary routes: one leading to the formation of essentials, while the other complemented the molecules, with the cooperative assembly of their constituents giving rise to modern RNAs.